The last trading week of 2015 begins on a historic precipice for stocks: as reported over the weekend, the U.S. stock market has not been lower for any year ending in a “5? since 1875. That streak is now in jeopardy, because following Thursday's shortened holiday session which ended with an abrupt selloff, the overnight session has seen continued weakness across global assets in everything from Chinese stocks which tumbled the most since November 27, to commodities (WTI is down 2.5%) to European stocks (Stoxx 600 -0.4%), to US equity futures down 0.4% on what appears to be an overdue dose of Santa Rally buyers' remorse.